Anatomy Nervous System Quiz

Functions of the nervous system

sensory input, integration, and motor output

Sensory input

To monitor changes occurring inside and

outside the body (stimuli)

Integration

• To process and interpret sensory input and

decide if action is needed

• This happens in the brain primarily

motor output

• A response to integrated stimuli

• The response activates muscles or glands

Central Nervous System (CNS)

• Brain

• Spinal cord

Peripheral Nervous System (PNS)

• Spinal nerves

• Cranial nerves

PNS: Sensory (afferent) division

• Nerve fibers that carry information to the

central nervous system

• Nerve fiber approach the CNS

PNS: Motor (efferent) division

• Nerve fibers that carry impulses away from the

central nervous system

• Nerve fibers exit the CNS

Subdivisions of the Motor (efferent) division

Somatic Nervous system (voluntary), Autonomic Nervous system (involuntary)

Somatic Nervous system

voluntary, skeletal muscles

Autonomic Nervous system

involuntary, cardiac and smooth muscle (Sympathetic nervous system = fight or flight, Parasympathetic nervous system = rest and digest)

Support cells in the CNS are grouped together as

Neuroglia (glial cells), their function is to support, insulate, and protect

Types of neuroglia (glial cells):

• Astrocytes

• Microglia

• Ependymal cells

• Oligodendrites - CNS only

• Schwann cells - PNS only

Types of neuroglia (glial cells): Astrocytes

• Abundant, star-shaped cells

• Brace neurons

• Form barrier between capillaries and neurons

• Control the chemical environment of

the brain

• Mop up leading potassium ions and

recapture neurotransmittors

Types of neuroglia (glial cells): Microglia

• Spiderlike phagocytes

• Dispose of debris like dead nerve cells and

bacteria

Types of neuroglia (glial cells): Ependymal cells

• Line cavities of the brain and spinal cord

• Circulate cerebrospinal fluid using beating

cilia

Types of neuroglia (glial cells): Oligodendrocytes

• Wrap around nerve fibers in the central

nervous system - CNS

• Produce myelin sheaths

Types of neuroglia (glial cells): Satellite cells

• Protect neuron cell bodies by cushioning the

cells

Types of neuroglia (glial cells): Schwann cells

• Form myelin sheath in the peripheral nervous

system

Neurons = nerve cells

• Cells specialized to transmit messages

Major regions:

• Cell body—nucleus and metabolic center

of the cell

Dendrites

conduct impulses toward the cell

body

Axons

conduct impulses away from the cell

body

Axonal terminals

are separated from the next

neuron by a gap

Axonal terminals: Synaptic cleft

gap between adjacent neurons

Axonal terminals: Synapse

junction between nerves

Neurotransmitters

chemicals that transmit an

impulse across a synapse to another cell, are found in tiny vesicles

(or bubbles of cell membrane) in the axon

terminal,

neurotransmitter ex

• Dopamine

• Adrenaline

• Endorphins

Myelin sheath

whitish, fatty material covering axons, produced by Schwann Cells

Nuclei

clusters of cell bodies within the white

matter of the central nervous system

Ganglia

collections of cell bodies outside the

central nervous system in the PNS

Tracts

are bundles of nerve fibers running

through the CNS

Nerves

are bundles of nerve fibers running

through the PNS

White matter

consists of dense collections of

myelinated fibers (tracts)

Gray matter

mostly unmyelinated fibers and cell

bodies

Sensory (afferent) neurons

Carry impulses from the sensory receptors to

the CNS

Cutaneous sense organs

• Pain receptors – perceive pain

• Meissner’s corpusles – perceives light

touch

• Pacinian corpusles – perceives deep

pressure

• Proprioceptors—detect stretch or tension

Motor (efferent) neurons

Carry impulses from the central nervous

system to viscera, muscles, or glands

Interneurons (association neurons)

• Found in neural pathways in the central

nervous system

• Connect sensory and motor neurons

Multipolar neurons

many extensions from the

cell body – most common type, they are all motor

neurons and association neurons

Bipolar neurons

one axon and one dendrite –

these are rare, found only in the eye and nose

Unipolar neurons

have a short single process

leaving the cell body – these are the sensory

neurons in the PNS ganglia

Irritability

Ability to respond to stimuli

Conductivity

Ability to transmit an impulse

Resting neuron

• The plasma membrane is polarized-

• Fewer positive ions are inside the cell than

outside the cell

Depolarization

• A stimulus depolarizes the neurons

membrane

• membrane allows sodium (Na+)

to flow inside the membrane

Action potential

• If the action potential (nerve impulse) starts, it

is propagated over the entire axon

• Impulses travel faster when fibers have a

myelin sheath

Repolarization

• Potassium ions rush out of the neuron after

sodium ions rush in, which repolarizes the

membrane

• The sodium-potassium pump, using ATP,

restores the original configuration

how: Impulses are able to cross the synapse to another

nerve

• Neurotransmitter is released from a nerves

axon terminal.

• The dendrite of the next neuron has receptors

that are stimulated by the neurotransmitter

• An action potential is started in the adjacent

neuron.

threshold

the minimum level of stimulus

that is required to cause an impulse in a neuron. (minimum = -70 mV.)

Reflex arc

direct route from a sensory neuron, to

an interneuron, to an effector

The reflex arc has 5 parts:

1. Sensory receptor

2. Sensory (afferent) neuron

3. Integration center

4. Motor (efferent) neuron

5. Effector organ